40 F. W. THYNG 



side is bilobate and somewhat removed from the prohferating 

 entoderm of the thyreoid, but on the left the two are intimately 

 connected. 



The thyreoid gland (plates 2 and 6) is distinctly U-shaped, with 

 the concavity of the U directed cephalad. The level of the slender 

 connecting bar of the median thyreoid (Thyr.m.) is seen in plates 

 1 and 6. The arms of the U, derivatives in part of the ultimo- 

 branchial bodies (which are still discernible although intimately 

 connected with the median thyreoid) are widened considerably 

 dor so-ventr ally, and terminate at a level corresponding with the 

 cephalic ends of the thymic cylinders. Numerous proliferating 

 cords of cells make its surface somewhat irregular. Its connec- 

 tion on the left with the parathyreoid anlage of the fourth pharyn- 

 geal pouch has been referred to above. 



Salivary glands. The parotid and submaxillary glands are 

 shown in plates 2 and 5. The parotid gland is represented by a 

 small, solid cord of cells {Gl.p.) partly constricted off from the 

 ridge leading caudad from the angle of the mouth and overlying 

 the sulcus buccalis. The submaxillary gland is represented by a 

 solid cord of cells (Gl.s.) but is larger than the parotid anlage. It 

 projects from the caudal part of the floor of the alveolo-lingual 

 groove into the underlying mesenchyma which for some space 

 around the gland consists of closely packed cells for the develop- 

 ment of a capsule. Its extremity is broader than the stalk, and 

 shows slight indications of proliferating buds. The anlagen of 

 the sublingual glands have not developed at this stage. That 

 they are the latest of the salivary glands to develop, has been 

 noted by His ('85), Chievitz ('85), Hammar ('01), Paulet ('10) 

 and others. 



Oesophagus. The oesophagus is comparatively long at this 

 stage. The entodermal part of the tube only is figured in plates 

 1 and 2. This consists of an epithelium, containing four or more 

 layers of nuclei. Numerous irregular cavities, as seen by Schultze 

 ('97), and others, are found within the epithelium. They occur 

 in scattered situations, and are separated from the surrounding 

 mesenchyma usually by a single layer of columnar or cuboidal 

 cells. In no case were they found to connect with the lumen of the 



